291+ EYE FIELD OPERATIONS 



EYE INDUCTIONS 



This is an extremely delicate operation (Mangold, 1951) and ahould be attempted by 

 only those students who have proven their skill In operative procedures. 



Gastnilae (Anura stages #10 and #12) are decapsulated. The donor (stage #12) Is dis- 

 sected so as to expose the most anterior portion of the archenteric roof. This material 

 la excised In one piece and la quickly Inserted through the hlastocoellc roof of the 

 younger (stage #10) gastrula (see diagrams). If the normal "Inductive" (see Gloasaiy) In- 

 fluences are exerted on the overlying ectoderm of the blastocoellc roof, accessory optic 

 structures will be formed. (See exercise on "The Organizer" for procedures.) 



TRANSPLANTATIONS 



Under this heading will be Included the simpler transplantations of optic cup and/or 

 lens primordlum In order to determine their interrelationship in the normal development of 

 the eye as a whole. There will also be Included the homoplastic, heteroplastic, and xeno- 

 plastic transplantations of larval eyes. 



LENS INDUCTION : (See Stone & Dinnean 1914-0 and Liedke I9U2) 



1. Remove the presumptive lens ectoderm from over the optic vesicle or cup of 

 Anuran stage #l6 or #17, (Urodela stages #21 to #26)* without injuring the 

 underlying structures. Quickly excise a slightly larger piece of belly ecto- 

 derm from another embryo, of the same stage previously stained with Nile Blue 

 Sulphate. Place it over the exposed optic vesicle. Gently pat it into place 

 and, if necessary, hold It in place with a Briicke, lens paper, or piece of 

 coveralip. It should heal within 20 to 30 minutes. (See section on "Wound 

 Healing" . ) 



2. Remove the ectoderm from over the optic vesicle of Anuran stage #17 (Urodela 

 stages #21 to #26)*. Prepare a host embiyo (of the same stage) by making a 

 deep pit ventral to the somites at about the mid-body region, leaving the flap 

 of ectoderm over the pit Intact. (See A-2-c \inder "Defect Experiments" on the 

 preceding page.) Quickly cut out the optic vesicle of the donor and transfer 

 it to the excavated pit of the host. Orient the vesicle in the same position 

 as in the donor, i.e., with the bulbous part of the vesicle facing outward. 

 Replace the ectodermal flap over the transplanted optic vesicle, and hold it in 

 place with Briicke until healed. 



These two experiments are reciprocally related. Part 1 will indicate 

 whether foreign (non-presumptive) ectoderm will respond to inductive Influences 

 from the Intact optic vesicle and Part 2 will indicate whether the optic 

 vesicle, transplanted to a foreign site, can there induce a lens in the over- 

 lying (foreign) ectoderm. All such embryos should be allowed to progress to 

 the external gill stage before dissection analysis. 



TRANSPLANT ATIONS : 



TRANSPLANTING THE ANLAGE 



When the anlage is transplanted to a slightly older host, the conditions for the 

 expression of any self-differentiation are somewhat different from those of an isola- 

 tion culture. However, the nutritive factors are generally the more favorable, and 

 eucial relations can be determined. These operations are best on Urodele embryos.** 

 1. Decapsulate some Urodele embryos in stage #11+, and locate the eye field at the 

 anterior limit of the medullary plate (see figure on following page). Stain 

 the entire donor In l/500,000 Nile Blue Sulphate. 



* After Urodele stage #26 (Anura stage #17) the potential lens forming ectoderm becomes ad- 

 herent to the underlying optic cup, and cannot be completely removed. The older embryos 

 can be anesthetized In MS 222. 



**Follow the standard operative procedures described elsewhere. See Schwind (1957) for 

 results with the Anura. 



